The height marker is to advise you not to turn to ff until they reach it. It's not to say when they reach it you need to turn them round. In countries like Sweden children stay rf until age 4. They have had no child fatalities in 50 years! Australia are not following best practice when it comes to car seats. It is 5 times safer to be rf than ff, and broken legs are better than broken necks to put it bluntly. To understand why - Google ff versus rf on you tube. I'd love to turn my bub round as he hates the seat but I can't after understanding the whole car seat thing now.